1. Field of the Invention
The present invention is directed generally to counterbalanced support arms and more specifically to a counterbalanced support arm used to support a lighthead suspended from a ceiling.
2. Description of the Prior Art
Counterbalanced support arms are well known and are used in such diverse applications as supporting robot arms and surgical lightheads. In surgical lighthead applications, two competing design criteria must be balanced. On the one hand, it is necessary for the surgical lighthead to remain fixed after being positioned by the surgeon or a member of the surgical team. On the other hand, the force needed to move the lighthead from one position to another must be as low as possible to enable very precise positioning with the least amount of force. It is clearly difficult to satisfy both those needs when suspending a sixty pound lighthead from the end of an arm. Thus, it is not uncommon in the art to find lightheads that tend to move from the position where they are placed without the application of external force due to the weight of the lighthead while other lightheads are too stiff to allow for minute adjustments.
Another problem area arises from limited maneuverability of the support arm. Because of new medical techniques, it is necessary to position lightheads used in certain healthcare facilities in positions heretofore not adequately addressed. For example, in some gynecological procedures, it is necessary for the lighthead, which is typically suspended from the ceiling, to be placed close to the floor and directed upwardly. The need for such a wide range of movement coupled with the need for the lighthead to be easily positioned throughout that range of movement without any drifting presents a difficult challenge to the design engineer.